Spherical electrode and electrolysis cell including same

ABSTRACT

The present invention relates to a spherical electrode and to a spherical electrode cell, and more particularly, to a method for forming an electrode on an ion-exchange resin or forming an electrolysis cell on an ion-exchange resin. The spherical electrode or spherical electrolysis cell of the present invention can be used for: electrolysis reactors, for example in hydrolysis for producing hydrogen and oxygen gas; for the production of oxidants by means of the electrolysis of electrolytes such as a sodium chloride solution and sodium chlorite; or fuel cells that generate electricity using oxygen and hydrogen.

TECHNICAL FIELD

The present invention relates to a spherical cell suitable for electrolysis of water or an aqueous solution of electrolyte (e.g. sodium chloride or sodium chlorite) or the like, and to an electrolysis cell including the same.

BACKGROUND ART

An electrochemical cell is a kind of energy conversion system. For example, such electrochemical cells may be classified into electrolysis cells producing oxygen or hydrogen gas by using reactants, such as water, or decomposing a solution containing sodium chloride or sodium chlorite electrolyte, and fuel cells generating electricity by using oxygen and hydrogen fuel.

Fundamental constitutional unit elements of an electrochemical cell include an anode, a cathode and an electrolyte. FIG. 1 shows a typical electrolysis cell, including an anode chamber 20 having an anode 10, a cathode chamber 40 having a cathode 30, and an ion-exchange membrane 50 serving as an electrolyte transfer medium between the anode and the cathode. The operation mechanism of such an electrolysis cell will be described by taking, as an example, an electrolysis cell in which NaClO₂ is supplied to the anode chamber as an electrolyte to produce chlorine dioxide. The electrolyte, NaClO₂, is supplied to the anode in the anode chamber, and then is decomposed into chlorine dioxide (ClO₂) gas, electron (e⁻) and sodium ion (Na⁺), while a non-reacted portion is discharged out of the anode chamber of the electrolysis cell together with chlorine dioxide (ClO₂) gas. After the decomposition, sodium ion (Na⁺) passes through the ion-exchange membrane 50 and moves toward the cathode 30 (hydrogen electrode), while electron moves along an outer path 60 by which the anode 10 and the cathode 30 are connected with each other. Pure water is supplied to the cathode chamber 40, and then decomposed at the cathode 30 by the electron (e″) transferred from the anode 10 (reduction). As a result, pure water is decomposed into hydrogen (H₂) gas and hydroxide ion. Hydroxide ion reacts with sodium ion transferred from the anode chamber 20 through the ion-exchange membrane 50, thereby forming NaOH. Herein, the electrochemical reactions occurring at the anode 10 and the cathode 30 separately may be represented by the following Reaction Formulae 1 to 4.

NaClO₂→Na⁺+ClO₂ ⁻ (dissociation of electrolyte at anode)  [Reaction Formula 1]

ClO₂ ⁻→ClO₂ (gas)+e ⁻ (oxidation at anode)  [Reaction Formula 2]

H₂O+e ⁻→1/2H₂+OH⁻ (reduction at cathode)  [Reaction Formula 3]

Na⁺+OH⁻→NaOH (production of sodium hydroxide at cathode)  [Reaction Formula 4]

In addition, the system of FIG. 1 may be applied to electrochemical decomposition of water to produce hydrogen gas and oxygen gas. In the system of FIG. 1, water (H₂O) is supplied to the anode catalyst, and then decomposed into oxygen gas (O₂), electron (e⁻) and proton (H⁺) by an electrochemical reaction. Herein, a portion of water is discharged out through the product outlet of the electrolysis cell together with oxygen (O₂) gas. Then, thus decomposed proton (H⁺) passes through the ion-exchange membrane and moves toward the cathode catalyst (hydrogen electrode), so that it may react with the electron (e) transferred along an external path (not shown) connected between the anode catalyst and the cathode catalyst to produce hydrogen (H₂) gas. Herein, the electrochemical reactions occurring at the anode catalyst and the cathode catalyst separately are represented by the following Reaction Formulae 5 and 6.

2H₂O→4H⁺+4e ⁻+O₂ (oxidation at anode)  [Reaction Formula 5]

4H⁺+4e ⁻→2H₂ (reduction at cathode)  [Reaction Formula 6]

Meanwhile, in a fuel cell, reactions occur through a mechanism opposite to the reaction mechanism of the above-described electrolysis of water. In other words, in a fuel cell, hydrogen, methanol or other hydrogen fuel sources react with oxygen to generate electricity. Herein, general reactions occurring in a fuel cell are represented by the following Reaction Formulae 7 and 8

2H₂→4H⁺+4e ⁻ (oxidation at anode)  [Reaction Formula 7]

4H⁺+4e ⁻+O₂→2H₂O (reduction at cathode)  [Reaction Formula 8]

In the above-mentioned electrochemical reactions (Reaction Formulae 2 & 3, Reaction Formulae 5 & 6, and Reaction Formulae 7 & 8), reactions occur at the interface of an electrode. At the interface of an electrode, a solid-liquid-gas three-phase reaction is involved. Particular phenomena involved herein include provision of an electron transfer path in a solid portion, transfer of ions to an electrode in a liquid as an electrolyte, transfer of a product (in the case of a liquid) to a bulk solution, and transfer of a gas product to a bulk solution in a gaseous portion. Therefore, to maximize the efficiency of an electrochemical reaction, it is required to maximize electrolyte transferability (conductivity), to maximize an electron transfer path (electrode area), and to maximize gas product transfer (electrode shape). As a result, a general electrochemical reactor, in which an electrode having a predetermined space takes a structure of a plate-like electrode or a mesh-like electrode, requires stacking of a plurality of electrodes, thereby limiting significant improvement in its performance.

FIG. 2 shows another embodiment of a typical electrolysis cell. In FIG. 2, a spherical electrode 26 is disposed between an anode 22 and a membrane 28, and between a membrane 28 and a cathode 24. Thus, the area of an electrode in the electrolysis cell is maximized as compared to the electrolysis cell shown in FIG. 1.

A particular example of patents related to a spherical electrode is U.S. Pat. No. 6,024,850 (Title: Modified Ion Exchange Materials, Applicant: Assignee: Halox technologies Corporation). The spherical electrode disclosed therein is characterized in that an ion-exchange resin is used as a matrix and an electrode catalyst is present in the ion-exchange resin.

However, such a spherical electrode having an electrode catalyst in an ion-exchange resin is functionally problematic, as described hereinafter with reference to FIG. 3 on the basis of the above-described reaction phenomena occurring at an electrode surface.

First, an electrolyte is transferred into an ion-exchange membrane to cause an electrochemical reaction, thereby causing degradation of reaction efficiency (this is because diffusion resistance is too high to transfer ions into the ion-exchange resin, and it is more difficult to transfer thus generated gas to the exterior of the ion-exchange resin).

Second, there is no electron transfer path (specifically, metal) for the electron formed by the electrochemical reaction in the ion-exchange resin, thereby increasing electron resistance and reducing reaction efficiency.

Moreover, in the case of an electrochemical reaction dealing with a high-concentration electrolyte, an electrode catalyst may be discharged, resulting in rapid degradation of durability. The electrode of the related art includes a structure having an electrode catalyst containing a counterion at the active site in the ion-exchange resin. Thus, when electrolyzing a high-concentration electrolyte, such as saturated brine, the catalyst ion may be discharged easily. This may be predicted easily from a regeneration process using brine in a general ion-exchange resin.

DISCLOSURE Technical Problem

The present invention is directed to providing a spherical electrode structure capable of being filled in an electrolysis cell and applicable to various conditions including electrolytes or concentration.

Technical Solution

In one general aspect, the present invention provides an electrode for an electrochemical cell including an ion-exchange resin matrix and a first electrode layer coated on a surface of the ion-exchange resin matrix, characterized in that the electrode has a shape selected from the group consisting of spheres, granules, beads, grains and fibers.

According to an embodiment, the first electrode layer may be coated on 1-100% of the total surface area of the electrode for an electrochemical cell. Particularly, a coating ratio of at least 70% is preferable in view of overall electrochemical performance or efficiency.

According to another embodiment, the electrode for an electrochemical cell further includes a second electrode layer, wherein the second electrode layer is coated on a surface of the ion-exchange resin matrix, and may be provided as a multilayer type electrode in which the first electrode layer is coated on a surface of the second electrode layer. In addition, the electrode for an electrochemical cell may further include a third electrode layer coated on a surface of the first electrode layer. Such a multilayer type electrode may exhibit electrode quality equal to or better than an electrode using a noble metal catalyst, while reducing the amount of an expensive noble metal catalyst significantly.

In another general aspect, the present invention provides an electrochemical cell including an ion-exchange resin matrix, a first electrode layer coated on a surface of the ion-exchange resin matrix, and a second electrode layer coated on the surface of the ion-exchange resin matrix, characterized in that the electrode has a shape selected from the group consisting of spheres, granules, beads, grains and fibers, and the first electrode layer and the second electrode layer correspond to an anode and a cathode, respectively, or to a cathode and an anode, respectively.

According to an embodiment, the first electrode layer and the second electrode layer have a combined surface area corresponding to 1-99%, particularly 30-90% of the total surface area of the electrode chemical cell. According to another embodiment, to provide the above-defined range of combined surface area, each of the first electrode layer and the second electrode layer may be coated on 0.5-60% of the total surface area of the electrochemical cell.

Particularly, when the first electrode layer and the second electrode layer have a combined surface area corresponding to 50-70% of the total surface area of the electrochemical cell, and each of the anode and the cathode is coated in such a manner that each surface area is 30-35% of the total surface area of the electrochemical cell, the resultant electrochemical cell is capable of normal operation even without a short-preventing medium, such as a non-woven web, between the anode and the cathode.

Controlling the surface coating degree of the electrode may be performed easily by those skilled in the art as long as it is based on the present disclosure.

The matrix may be selected from the group consisting of: strongly acidic crosslinked polystyrene-divinylbenzene cationic resins; weakly acidic crosslinked polystyrene-divinylbenzene cationic resins; iminodiacetic acid-chelated crosslinked polystyrene-divinylbenzene cationic resins; strongly basic polystyrene-divinylbenzene anionic resins; weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic acrylic anionic resins; strongly acidic perfluorosulfonated cationic resins; strongly basic perfluroroaminated anionic resins; natural anion exchangers; natural cation exchangers; porous inorganic materials; and combinations thereof.

The first electrode layer may be selected from the group consisting of platinum group metals (platinum, ruthenium, rhodium, palladium, osmium, iridium), as well as gold, silver, chrome, iron, lead, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, tin and alloys or combinations thereof. The second electrode layer may be selected from the group consisting of titanium, silver, copper, tin and alloys or combinations thereof. In addition, the first electrode layer may have a thickness of 0.1-5 μm.

In still another general aspect, the present invention provides a hollow sphere electrode capable of being filled between an anode and a cathode, between an anode and a membrane, between a cathode and a membrane, between a membrane and a membrane, or the like, in an electrolysis cell for an aqueous solution containing an electrolyte, characterized in that the electrode is filled in such a manner that the electrode has an area of 1,000-1,000,000 cm² per m³ of volume of the electrolysis cell.

According to an embodiment, the hollow sphere electrode has a structure in which a metal is precipitated as an electrochemical catalyst on a surface of a medium capable of ion exchange in an amount of 1-100%.

The electrolysis cell includes a medium capable of ion exchange, and at least one metal precipitated as an electrochemical catalyst on a surface of the medium at a ratio of 1-99%.

Advantageous Effects

The electrode according to an embodiment has an electrode surface area up to 100 m² per m³ of an electrolysis cell, and thus maximizes the performance of an electrolysis system, makes an electrolysis system compact, and reduces manufacturing cost.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a typical electrolysis cell;

FIG. 2 is a schematic view showing another typical electrolysis cell (U.S. Pat. No. 6,024,850 (Title: Modified Ion Exchange Materials, Applicant: Assignee: Halox Technologies Corporation);

FIG. 3 is a schematic view illustrating a problem of the electrolysis cell as shown in FIG. 2;

FIG. 4 is a schematic view showing a spherical electrode 400 according to an embodiment of the present invention;

FIG. 5 is a schematic view showing a spherical electrode 500 having a multilayer type metal layer according to another embodiment of the present invention;

FIG. 6 is a schematic view showing a spherical electrode according to still another embodiment of the present invention;

FIG. 7 shows a spherical electrochemical cell 700 according to an embodiment of the present invention;

FIG. 8 is a scanning electron microscope (SEM) image of a first Ti coating layer obtained from Example 9;

FIG. 9 is an SEM image of a second Pt coating layer obtained from Example 9;

FIG. 10 is an X-ray diffraction (XRD) image of the sample obtained from Example 9;

FIG. 11 is a schematic view showing the electrolysis cell according to an embodiment of the present invention;

FIG. 12 is a graph showing the results of comparison of the electrode of the present invention with the electrode according to a comparative example in terms of electrolysis voltage;

FIG. 13 is a graph showing the results of comparison of the electrode of the present invention with the electrode according to a comparative example in terms of chlorine concentration;

FIG. 14 is a graph showing the results of comparison of the electrode of the present invention with the electrode according to a comparative example in terms of current efficiency;

FIG. 15 is a photo showing the spherical electrolysis cell of FIG. 7; and

FIG. 16 is a photo showing a magnified view of the interface of the spherical electrolysis cell of FIG. 10.

BEST MODE

Hereinafter, the embodiments of the present disclosure will be described in detail with reference to accompanying drawings.

FIG. 4 is a schematic view showing a spherical electrode 400 according to an embodiment. As shown in FIG. 4, the spherical electrode 400 uses an ion exchanger as a matrix 410 and includes an electrode catalyst 420 on the surface of the matrix. However, the shape of the matrix is not limited to a particular shape, such as a spherical shape.

The matrix 410 may be any medium capable of ion exchange. Particular examples of the matrix material include: strongly acidic crosslinked polystyrene-divinylbenzene cationic resins; weakly acidic crosslinked polystyrene-divinylbenzene cationic resins; iminodiacetic acid-chelated crosslinked polystyrene-divinylbenzene cationic resins; strongly basic polystyrene-divinylbenzene anionic resins; weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic acrylic anionic resins; strongly acidic perfluorosulfonated cationic resins; strongly basic perfluroroaminated anionic resins; natural anion exchangers, such as clay; natural cation exchangers, such as manganese greensand; porous inorganic materials, such as zeolite, capable of absorbing ions; and combinations thereof. Such matrix materials are commercially available.

The catalyst 420 coated on the matrix may be selected from the group consisting of platinum group metals (platinum, ruthenium, rhodium, palladium, osmium, iridium), as well as gold, silver, chrome, iron, lead, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, tin and alloys or oxides thereof.

Although there is no limitation in thickness of the electrode catalyst layer 420, the electrode catalyst layer may have a thickness of 0.1-5 μm, more particularly 0.1-2 μm. In the case of a thickness greater than 2 μm, a non-active reaction layer that does not participate in a reaction becomes too thick, thereby causing catalyst loss and poor cost efficiency.

The electrode catalyst layer 420 may have a surface area covering 1-100% of the surface of the matrix depending on the particular purpose of electrochemical reaction.

Methods for forming the electrode catalyst layer on the ion exchange resin body include chemical methods, such as adsorption-reduction and electroplating, physical methods, such as vacuum deposition, etc. However, considering coating on a large amount of spherical ion exchanger particles, chemical adsorption-reduction methods may be used. Chemical adsorption-reduction methods are carried out by allowing an electrode catalyst material to be adsorbed on an ion exchange resin and reducing the electrode catalyst material on the surface of the ion exchange resin. Such methods may be applied and performed easily by those skilled in the art.

FIG. 5 shows a spherical electrode 500 having a multilayer type metal layer according to another embodiment of the present invention. After forming a first metal layer 520 on the ion exchange resin matrix 510 as shown in FIG. 4 by an adsorption-reduction method, or the like, the same or different metal catalyst layer 530 is further formed on the first metal layer to provide an electrode having a bilayer structure. The first layer 520 may include a metal, such as titanium, silver, copper or tin, having excellent electron conductivity. The second layer 530 may include the electrode catalyst layer as mentioned with reference to FIG. 4.

FIG. 6 is a schematic view showing a spherical electrode according to still another embodiment. The spherical electrode is a hollow spherical electrode structure obtained by firing the spherical electrode as shown in FIG. 4 or FIG. 5 at about 800° C. so that the inner ion exchange layer is pyrolyzed.

FIG. 7 shows a spherical electrochemical cell 700 according to an embodiment. As shown in FIG. 7, the sphere functions as a unit electrolysis cell 700. The spherical electrochemical cell 700 includes fundamental elements of an electrochemical cell, such as an anode, cathode, electrolyte, or the like. The spherical electrochemical cell includes an ion conductor matrix 710 as an electrolyte, a metal 720 having an anodic function (oxidation) as an anode catalyst, and a metal 730 having a cathodic function (reduction) as a cathode catalyst. Particular types of the anode catalyst 720 or cathode catalyst 730 coated on the matrix are the same as described with reference to FIG. 4. In practice, the metal forming the anode catalyst 720 may be different from the metal forming the cathode catalyst 730.

In the spherical electrochemical cell, the electrode catalyst layer may have a thickness of 1-5 μm. In the case of a thickness greater than 5 μm, a non-active reaction layer that does not participate in a reaction becomes too thick, thereby causing catalyst loss.

The surface area (combined surface area of the anode layer surface with the cathode layer surface) may be within a range of 1-99% depending on the particular purpose of electrochemical reaction. More particularly, the surface area (combined surface area of the anode catalyst surface with the cathode catalyst surface) may be within a range of 30-90%. The surface area that equals to 100% means a contact between the anode and the cathode, suggesting a short between the anode and the cathode as a physical meaning. Thus, in this case, no electrochemical reaction occurs.

Methods for forming the anode catalyst metal 720 and the cathode catalyst metal 730 are the same as described above with reference to FIG. 4. For example, a metal catalyst as the anode catalyst metal 720 is formed first partially on the total surface by an adsorption-reduction method, and then the cathode catalyst metal 730 is further formed partially on the total surface by an adsorption-reduction method. Since an adsorption-reduction method is used, it is possible to form the anode catalyst metal 720 and the cathode catalyst metal 730 at different positions.

FIG. 15 is a photo showing the spherical electrolysis cell of FIG. 7, wherein Pt is used as an anode catalyst metal and Sn is used as a cathode catalyst metal. FIG. 16 is a photo showing a magnified view of the interface of the spherical electrolysis cell of FIG. 10.

MODE FOR INVENTION

The examples and experiments will now be described. The following examples and experiments are for illustrative purposes only and not intended to limit the scope of the present disclosure.

Examples 1-10 Manufacture of Spherical Electrodes

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Catalyst type Pt Ru Ni Pd Precursor type Pt(NH₃)₆]Cl₄ RuCl₄ NiCl₂ PdCl₂ Precursor 1 mM 1 mM 1 mM 1 mM concentration Adsorption time 1 hr 1 hr 1 hr 1 hr Reducing agent NaBH₄ NaBH₄ NaBH₄ NaBH₄ type Reducing agent 5% 5% 5% 5% concentration Reduction time 1 hr 1 hr 1 hr 1 hr Reduction pH 8 8 8 8 Determination of SEM SEM SEM SEM precipitation Result Surface Surface Surface Surface coating coating coating coating

TABLE 2 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Catalyst type Ir Pb Sn Cu Precursor type IrCl₄ Pb(SO₄) SnCl₄ CuSO₄ Precursor 1 mM 1 mM 1 mM 1 mM concentration Adsorption time 1 hr 1 hr 1 hr 1 hr Reducing agent NaBH₄ NaBH₄ NaBH₄ NaBH₄ type Reducing agent 5% 5% 5% 5% concentration Reduction time 1 hr 1 hr 1 hr 1 hr Reduction pH 8 8 8 8 Determination of SEM SEM SEM SEM precipitation Result Surface Surface Surface coating Surface coating coating coating

TABLE 3 Ex. 9 Ex. 10 Catalyst type Pt/TiO₂ Pt (Anode), Ni (Cathode) Precursor type TiCl₄(1st) Pt(NH₃)₆]Cl₄NiCl₂ H₂PtCl₆(2nd) Precursor 1 mM 1 mM/1 mM concentration Adsorption time 1 hr 1 hr Reducing agent NaBH₄ NaBH₄ type Reducing agent 5% 5% concentration Reduction time 1 hr 1 hr Reduction pH 8 8 Determination of SEM SEM precipitation Result Surface coating Surface coating

FIG. 8 is an SEM image showing the first Ti coating layer obtained from Example 9. It is shown that Ti is developed well with a uniform shape.

FIG. 9 is an SEM image showing the second Pt coating layer obtained from Example 9. It is shown that Pt is not concentrated locally but is dispersed uniformly.

FIG. 10 is an image of the sample obtained from Example 9 taken by XRD analysis. It is shown that Pt, TiO₂ and the like are formed desirably. It is thought that Ti present in the form of TiO₂ results from oxide formation with oxygen in water.

Example 11 Preparation of Chlorate Ion Using Spherical Pt/TiO₂ Ion Exchange Resin (Matrix)

1. Manufacture of Spherical Electrode (see Example 9)

2. Structure of Electrolysis Cell

(1) Schematic View of Electrolysis Cell: FIG. 11

(2) Structural Parameters of Electrolysis Cell

TABLE 4 Parameter Value Presence of diaphragm No Distance between anode and 4 mm cathode Type and size of anode IrO₂—RuO₂ pyrolyzed electrode current collector on Ti, 4 cm × 4 cm Type and size of cathode Pt electroplated electrode on current collector Ti, 4 cm × 4 cm Short-preventing member on Nylon polymer-based nonwoven web with cathode current collector a porosity of 80% Position of filled electrode Filled in a 4 mm space between an anode and a cathode

3. Operation Condition of Electrolysis Cell

TABLE 5 Parameter Value Current density 0.1 A/cm² Electrolyte 3% aqueous NaCl solution Electrolyte retention time (min) 10

4. Analysis of Performance

(1) Method of Calculating Current Efficiency

Current efficiency is obtained by dividing a measured value of hypochlorous acid generated under an applied current (I) by a theoretical value according to the following formula:

Current efficiency (%)={(F×ρ×V)/(35500 (mg)×l×t)}×100,

wherein F is the Faraday constant (96500 (C)), ρ is an actual residual chlorine concentration (ppm, mg/L), V is a volume (L) of water supplied to an electrolysis cell, I is an applied current (A), and t is a time (s) of electrolysis.

(2) Performance parameters and Determination Methods

TABLE 6 Analysis Parameter Analysis method interval (hr) Results Voltage Determined by a 1 hr Expressed as Ex. multimeter 11 in FIG. 11 Chlorine Iodometry 1 hr Expressed as Ex. concentration 11 in FIG. 12 Current efficiency Calculated 1 hr Expressed as Ex. according to 11 in FIG. 13 Formula 1

Comparative Example 1 Preparation of Chlorate Ion Using Known Electrolyte Cell

1. Structure of Electrolysis Cell

TABLE 7 Parameter Value Presence of diaphragm No Distance between anode and 4 mm cathode Type and size of anode current IrO₂—RuO₂ pyrolyzed electrode on Ti, collector 4 cm × 4 cm Type and size of cathode current Pt electroplated electrode on Ti, collector 4 cm × 4 cm Short-preventing member on None cathode current collector Position of filled electrode None

2. Operation Condition of Electrolysis Cell

TABLE 8 Parameter Value Current density 0.1 A/cm² Electrolyte 3% aqueous NaCl solution Electrolyte retention time (min) 10

3. Performance Analysis

TABLE 9 Analysis Parameter Analysis method interval (hr) Results Voltage Determined by 1 hr Expressed as multimeter Comp. Ex. 1 in FIG. 11 Chlorine Iodometry 1 hr Expressed as concentration Comp. Ex. 1 in FIG. 12 Current efficiency Calculated 1 hr Expressed as according to Comp. Ex. 1 in FIG. Formula 1 13

As shown in FIG. 11, the electrode according to the present invention has the same electrolysis voltage as the electrode according to Comparative Example. Referring to FIG. 12, the electrode according to the present invention has a chlorine concentration two times higher than a chlorine concentration of the electrode according to Comparative Example. It is thought that such a higher current density is derived from a larger electrode area in the same space and a lower current density at a filled electrode. FIG. 13 illustrates comparison of the current efficiencies between the electrode according to the present invention and the electrode according to Comparative Example. The current density values are obtained from the results of FIG. 10 and FIG. 11 and the formula of current density as mentioned in Comparative Example 1. 

1. An electrode for an electrochemical cell, comprising an ion-exchange resin matrix and a first electrode layer coated on a surface of the ion-exchange resin matrix, characterized in that the electrode has a shape selected from the group consisting of spheres, granules, beads, grains and fibers.
 2. The electrode for an electrochemical cell according to claim 1, wherein the first electrode layer is coated on 1-100% of a total surface area of the electrode for an electrochemical cell.
 3. The electrode for an electrochemical cell according to claim 2, which further comprises a second electrode layer, wherein the second electrode layer is coated on a surface of the ion-exchange resin matrix, and the first electrode layer is coated on a surface of the second electrode layer.
 4. The electrode for an electrochemical cell according to claim 3, which further comprises a third electrode layer coated on a surface of the first electrode layer.
 5. The electrode for an electrochemical cell according to claim 3, wherein the matrix is selected from the group consisting of: strongly acidic crosslinked polystyrene-divinylbenzene cationic resins; weakly acidic crosslinked polystyrene-divinylbenzene cationic resins; iminodiacetic acid-chelated crosslinked polystyrene-divinylbenzene cationic resins; strongly basic polystyrene-divinyl benzene anionic resins; weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic acrylic anionic resins; strongly acidic perfluorosulfonated cationic resins; strongly basic perfluroroaminated anionic resins; natural anion exchangers; natural cation exchangers; porous inorganic materials; and combinations thereof, the first electrode layer is selected from the group consisting of platinum group metals (platinum, ruthenium, rhodium, palladium, osmium, iridium), as well as gold, silver, chrome, iron, lead, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, tin and alloys or combinations thereof, the second electrode layer is selected from the group consisting of titanium, silver, copper, tin and alloys or combinations thereof, and each of the first electrode layer and the second electrode layer has a thickness of 0.1-5 μm.
 6. An electrochemical cell comprising an ion-exchange resin matrix, a first electrode layer coated on a surface of the ion-exchange resin matrix, and a second electrode layer coated on the surface of the ion-exchange resin matrix, characterized in that the electrode has a shape selected from the group consisting of spheres, granules, beads, grains and fibers, and the first electrode layer and the second electrode layer correspond to an anode and a cathode, respectively, or to a cathode and an anode, respectively.
 7. The electrochemical cell according to claim 6, wherein the first electrode layer and the second electrode layer have a combined surface area corresponding to 1-99% of the total surface area of the electrode chemical cell, and each of the first electrode layer and the second electrode layer is coated on 0.5-60% of the total surface area of the electrochemical cell.
 8. The electrochemical cell according to claim 7, wherein the matrix is selected from the group consisting of: strongly acidic crosslinked polystyrene-divinylbenzene cationic resins; weakly acidic crosslinked polystyrene-divinylbenzene cationic resins; iminodiacetic acid-chelated crosslinked polystyrene-divinylbenzene cationic resins; strongly basic polystyrene-divinylbenzene anionic resins; weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic acrylic anionic resins; strongly acidic perfluorosulfonated cationic resins; strongly basic perfluroroaminated anionic resins; natural anion exchangers; natural cation exchangers; porous inorganic materials; and combinations thereof, the first electrode layer is selected from the group consisting of platinum group metals (platinum, ruthenium, rhodium, palladium, osmium, iridium), as well as gold, silver, chrome, iron, lead, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, tin and alloys or combinations thereof, and the first electrode layer has a thickness of 0.1-5 μm. 